Time delay electrical relay system



Sept. 1949- w. H. BLANKMEYER 2,482,397

TIME DELAY ELEGTRICAL RELAY SYSTEM Filed June 21, 1945 A TTORNEYS.

Patented Sept. 20,1949

I V UNITED STATES PATENT OFFICE I TIME DELAY ELEGTRICAL'RELAY SYSTEM I WallacejH. Blankmeyer, Butte, Mont.

Application June 21, 1945, Serial No. 600,738

' 1 claim. (01. 115-420)] 1 My invention relates to timing devices and relates more particularly to timing devices which controlan electricalcircuit. A general object of this invention is to provide a timing device which does not require a separate controlling or timeinterval initiating circuit. More specifically then, theobjects of this invention are; first, to provide an interval initiating method whch is an integral part of the electrical load circuit, thereby eliminating the necessity of a separately wired and actuated initiating circuit; second, to promote simplicity of installation and operation of interval timers; and third, to provide a timing circuit which inthe manufactured article will be particularly adaptable for controlling existing equipment and at the same time will be more easily adapted to new equipment requiring a timing control.

'Among many applications for this invention is that of timing photographic printing operations. In this field, the timing device when attached to photographic printers requires no additional wiring of control circuitsbecause the switch normally used to operate printer lights is now capable of initiating timing intervals in the timing device The timing device in turn controls the printer lights according to previously established time-interval settings.

The drawing is a diagram of an electroniccircuit, which is one method among several possible methods of accomplishing the desiredtiming control function. V

In the drawing and following description, the timing device as applied electronically,comprises these parts and operations. I An electrical power source, of alternating current is applied across the points designated as In and l bon the drawing. 2 is a capacitor which is in series with the filament-cathode 3 of electron tube 4. Capacitor 2 provides the'reactance necessary to limit filament current to rated values for the specific tube used. The capacitor and tube chosen are selected so that the largest. portion of applied alternating voltage appears across the capacitor and the smallest portion appears across the tube filament. Thus the filament (hereafter called the cathode) has a comparatively low voltage difference across the twoterminals and can be considered as a unit with reference to the anode 8 of the tube. Cathode 3 then is considered for purposes-oi explanation and from the practical operating condition to have, throughout, the same potential as point lb to which the cathode is directly connected. The

cathode is considered solely as a source of emitted 2 electrons which will be collected by the anode 6 and in some conditions by control grid l8.

Relay 5 is energized by current flowing through it as a result of electron emission from cathode 3 to anode 6 during power half-cycles when la is positive and lb is negative. This current can flow only when conditions within tube'4 permit. The reverse power half-cycles are unusedwith respect to relay energization. Assuming relay 5 to be energized as shown, then the current through the relay coils will hold the relay contact 'l away from contactB and contact 9 away from contact l0. Lamp ll represents the electrical load circuit of the equipment to be controlled by the timer. Lamp ll can be energized for operation only during portions of the timing cycle when relay 5 allows contacts I and 8 to touch. Contacts 9 and l0 also touch at the same moment I and 8 touch.

I3 is a resistance having an ohmic value several times greater than any load lamp which will be used at ll. With conditions as shown, resistance I3 is in series with load II when relay 5 is energized. This latter condition exists after the completion of a timing cycle and a quiescent lstate remains until another cycle is started. Tracing through the series connection of resistor l3 and load ll, start at lb (one A. C. power connection) go through load ll and load switch l2. (which is closed), through push button switch l5 (which is held closed by spring pressure) to the junction point of resistors l3 and I4, through resistor l3 and back to the other A. C. power terminal la. In this condition, the greater portion of the applied A. C. voltage appears across resistor l3 and the lesser portion of the voltage appears across load ll, because l3 resistor has a much higher resistance than the load ll. As established by design, the value of resistor I3 is very high compared with load ll so that the magnitude of current flowing through those circuit elements is so low that there is no apparent effect upon the load equipment I I.

Now, since load I l connects on one side directly to lb and since the voltage drop across load ll is low compared to the voltage appearing across resistor l3, this places junction of resistors l3 and I4 nearer the potential of lb. Junction of resistors l3 and I4 connects through l4, variable. resistance It (across which is condenser IT), to control grid l8 of tube 4. Because grid l8 connect's back to junction of resistors l3 and I4, the grid is held at low potential with respect to cathode {l since 3 ties directly to lb and only a comparatively low potential exists across load ll which ties junction of resistors I 3 and I4 back to point Ib.

So far, conditions have been as shown in the drawing with power on the half cycles when lb is negative, entering at I b, flowing through to cathode 3 into the electron stream emitted from cathode 3 (assuming current flow to be in the direction of electron flow) to anode 6, through relay coil 5 and back to the positive side of power Ia.

As established earlier, the potential difference between grid is and cathode 3 is held low by the low potential drop across load II. Under this condition, tube 4 conducts on'all half cycleswhen cathode 3 is negative and anode 6 is positive. This rectified A. C. maintains relay coil 5 in the energized position.

To prepare for a timing interval, switch I2 is opened. With switch I2 open, junction of resistors I3 and I4 is no longer held near the potentialof point lb. Junction of resistors I3-and I4 now has no tie to lb but it is tied :to la through resistor I 3. This now places resistors I4, I6, condenser I? and grid I8 at a .potential approaching that of la while cathode 3 is connected to lb. Consequently, when lb is negative and Iais positive, current will flow through the circuit starting at lb, to cathode 3 through the electron stream to grid I8 through resistor I6, resistor I4 and resistor I3 to point Ia. After a few half cycles of this grid rectification, condenser ll will become charged to nearly the peak A. C. voltage from the power source. The charge across condenser I l is developed by the dropacross resistor I6 as a result of the rectified current passing through it from grid I8. Current magnitudes in this circuit are of very low order so that proper action can take place through resistor I3 which has a resistance high compared to load II but low compared to grid circuit values.

With the entire circuit in this present condition where switch I2 is open, both grid and anode rectification takes place andrelay coil 5 remains energized by current from the anode rectification. Condenser I? is charged with the negative side toward grid I3 and positive toward resistor I4 which connects back through resistor I3 to point Ia. Thus, since the grid network connects back to la which is also the anode side of the circuit, grid I8 has no ability in this condition,

to prevent the passage of electrons from cathode 3 to anode 6.

Now to start a timing cycle, switch I2 will be closed. This brings the junction of resistors I3 and I A closer to the potential of Ib because of the comparatively low resistance of load II which ties back to lb. This new condition places the positive side of condenser I! through resistor I4 and load II back to cathode 3 while the negative side of condenser I'l remains on grid I8. Grid I3 is now highly negative with respect to cathode 3 so that electrons can not pass from cathode 3 to anode l5 and relay 5 deenergizes. With relay 5 deenergized, relay contact I closes to contact 8 and relay contact 9 closes to contact I0. When relay contacts 7 and 8 touch, current can flow from Ia through contacts 1 and 3 through closed switch I2, through load II back to lb on both half cycles of power. This places the load II in an operating condition. With relay contacts '9 and I9 closed, the junction of I4 and I6 resistors is connected to lb and to the cathode 3 bringing the positive side of condenser I! to cathode 3. The negative sideof condenser I! is on thegrid :I 8.

Resistor it which is variable to adjust the timing device to the desired time interval, is of a very high ohmic value so that the discharge time of condenser I! through resistor I6 is sufficiently slow to accomplish the timing function. Actually the current discharging through resistor I6 from condenser I7 will be down to a few micro-amperes before the voltage across resistor I6 becomes low enough to allow electrons to pass from cathode 3 to anode 6. When electrons resume passing from cathode 3 to'anode 6, rectified current again energizes relay 5 which opens contacts I and 8 and load II becomes deenergized in the active state. Relay contacts 8 and I0 also open which places load II in series with resistor l3. A complete timing interval has transpired and the circuit is now again in the quiescent state which holds until another timing interval is started by opening and closing switch I2. Timing intervals can also be started by momentarily opening pushbutton switch I5 which has the same function electrically as .load switch I2 except that I5 is located on the timer for convenience when load switch 12 might be at a distance from the timer or for some other reason might be inaccessible.

Resistor I4 is an isolating element which .pre vents placing a direct short circuit across points In and lb when relay contact I closes to contact 8 and contact 9 closes to contact II]. Full power voltage is applied to resistor I4 when a timing interval is proceeding. Tracing this circuit through, start at Ia, through contacts 1 and I through switch I5 and resistor I4, through contacts I9 and 9 to point I b (relay contacts are closed during a timing interval). As chosen by design requirements, resistor I4 has an ohmic value capable of limiting the current through it to a low amount of heat dissipation but still does not interfere with the final voltage across :condenser-:I'I as a result of grid rectification during the time that switch I2 is open for preparing "the circuit for a timing interval.

This timing device allows'full and normal use of the switch originally installed for controlling the connected load, and in addition provides an adjustable timing function.

I .do not limit myself to the specific circuit design shown and described because there are several ways of causing a load circuit to also act as the starting or initiating circuit of a timing device.

I am aware of the various existing forms of timing arrangements. These arrangements accomplish the timing cycle initiation through a separate action or switch, this switch requiring a separate circuit devoted partially or entirely to the initiating function.

I claim:

In'an electricaltiming device using an electron tube having a cathode grid and anode with the cathode energized through a series voltage dropping capacitor, said capacitor connected in series with the cathode and from the anode side of an external alternating current source with the cathode returned to the other side of the A. C. source, said tube having an input circuit connected between cathode and grid, and an output circuit connected cathode and anode, a relay energized from said output circuit, said relay having two pairs of contacts arranged to be open when relay is energized, first pair of said contacts being in series with any external load to be energized for a time interval, said A. C. source to timing device to supply said external load throughsaid first contact pair, second "con; -tact gpair being connected .in series from cathode side of A. C. source to a capacitor shunted by an adjustable resistor, said capacitor and resistor combination hereafter referred to as the discharge circuit, said discharge circuit being in series with the connection to tube grid, junction point of second contact pair and discharge circuit being returned through two high value series resistances to anode side of A. C. source, said discharge circuit is thereby efiectively connected to anode side of A. C. source except when second contact pair closes to return discharge circuit to cathode side of A. C. source, junction of said two series resistances connects with load side of first contact pair with other side of said load returning to cathode side of A. C. source, thus said load becomes part of the tube input circuit as long as relay contacts remain open, said load circuit being of comparatively low impedance in reference to said two high value resistances maintains the input circuit effectively near cathode potential as long as load circuit continuity exists, opening said load circuit at any point then permits the input circuit to assume potential of anode side of A. C. source through said series resistances, said potential difference existing across grid and cathode results in grid rectification and storing of a potential in said discharge circuit capacitor, said potential across discharge circuit having negative polarity toward the tube grid, said potential being more than sufficient to reduce or block the tube anode current in the output circuit when positive side of discharge circuit is returned to tube cathode, said return to cathode being accomplished by closing external load circuit, said potential across discharge circuit now blocks anode current in output circuit, releasing relay contacts to closed position, said first contact pair energizes external load circuit, said second contact pair connects cathode side of A. C. source to junction of discharge circuit and the two series resistances, said energization of external load continues until potential in discharge circuit capacitor discharges through said adjustable resistance until discharge circuit potential is no longer suflicient to block the anode current, relay is then energized thus opening contacts to deenergize external load at end of timing intervaLsaidtimingintervalcaninitiate at any time by opening and closing external load circuit at any point, length of said timing interval to be predetermined by the rate of dis charge from discharge circuit capacitor as set on adjustable resistance across said capacitor.

WALLACE H. BLANKMEYER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,238,987 Albin Apr. 22, 1941 2,249,488 Nickle July 15, 1941 2,339,750 Bartholy Jan. 25, 1944 2,368,477 Kinsman Jan. 30, 1945 2,396,497 Eisen-berg Mar. 12, 1946 2,433,845 Hayes Jan. 6, 1948 

